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CWDA No. 2 <br />#01349-0001 7 ]H[uddlrston Berry <br />07/19/17 117 Lnpnc.rinsS Tn inp LLC <br />Discussion of Inclinometer Monitoring <br />As indicated in the 1St Quarter 2017 report, some minor movement was observed in the data for <br />BG05. However, the 211d Quarter 2017 monitoring data profile returned to match the earlier data <br />sets. This suggests that the previously observed movement was in -fact due to a measurement <br />error as hypothesized in the referenced 1St Quarter report. In general, the 211d Quarter 2017 <br />monitoring data does not provide any indication of instability in CWDA No. 2. <br />Vibrating Wire Piezometers <br />Between 2005 and 2012, a total of ten vibrating wire piezometers were installed in CWDA No. <br />2. However, several of the piezometers have been damaged or have otherwise ceased to <br />function. Currently, five of the piezometers are functional. <br />Monitoring of the functioning piezometers was completed by DOWL on June 26th, 2017. The <br />attached monitoring report prepared by DOWL includes the piezometer monitoring data and the <br />data is summarized in the following table. <br />VWP ID <br />Initial Pore <br />Pressure <br />(psi) <br />03/10/17 Pore <br />Pressure <br />(psi)(psi) <br />06/26/17 Pore <br />Pressure <br />Difference Since <br />Installation <br />(psi) <br />Difference <br />Since Last <br />Reading (psi) <br />VWP-05 <br />6.8 <br />1.9 <br />1.9 <br />-4.9 <br />0.0 <br />VWP-06 <br />11.3 <br />13.6 <br />13.3 <br />+2.0 <br />-0.3 <br />VWP-08 <br />1 8.2 <br />9.8 1 <br />9.7 <br />+1.6 <br />1 -0.1 <br />VWP-09 <br />1 2.8 <br />2.9 1 <br />2.9 <br />+0.1 <br />1 0.0 <br />VWP-10 <br />1 -1.9 <br />-1.7 1 <br />-1.7 <br />+0.2 <br />1 0.0 <br />Discussion of Vibrating Wire Piezometers <br />VWP-05 <br />VWP-05 was installed on August 3, 2005 near the toe of CWDA No. 2 adjacent to the access <br />road/bench. The pore pressures recorded at VWP-05 have shown some seasonal fluctuations; <br />however, the range of pore pressure changes is fairly small. In general, HBET does not believe <br />that the pore pressures in VWP-05 are cause for concern regarding stability of the gob pile. <br />IMT <br />VWP-06 was installed on June 5, 2009 near the existing top of CWDA No. 2. The pore <br />pressures recorded at VWP-06 have fluctuated since installation. In general, the fluctuations <br />have been seasonal and reflect the level of coal mine waste placement activity on top of CWDA <br />No. 2. In general, HBET does not believe that the measured pore pressures are an indication of <br />any instability in CWDA No. 2. <br />VWP-08 <br />VWP-08 was installed on June 5, 2009 at a slightly lower elevation than VWP-06. The pore <br />pressures recorded at VWP-08 have fluctuated since installation. However, the fluctuations have <br />generally been within a narrow range of values. The measured pore pressures are generally <br />consistent with the level of coal mine waste placement activity at CWDA No. 2. <br />As indicated in the referenced Stability Evaluation report, the stability of CWDA No. 2 is <br />sensitive to increases in pore pressures in VWP-08. An increase in the pore pressure of 7 psi in <br />VWP-08 would result in a reduction of the Factor of Safety to below 1.5. <br />X:\2008 ALL PROJECTS\01349 -Bowie Resources, LLC\01349-0001 Bowie Mine\200 - Geo\Gob 2\Instrumentation Monitoring\2017\01349-0001 GP2 2ndQ 2017 L071917.doc 2 <br />